/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.servlet.tags;

import java.beans.PropertyEditor;
import javax.servlet.jsp.JspTagException;
import javax.servlet.jsp.PageContext;

import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.validation.Errors;
import org.springframework.web.servlet.support.BindStatus;

/**
 * The {@code <bind>} tag supports evaluation of binding errors for a certain
 * bean or bean property. Exposes a "status" variable of type
 * {@link org.springframework.web.servlet.support.BindStatus},
 * to both Java expressions and JSP EL expressions.
 *
 * <p>Can be used to bind to any bean or bean property in the model.
 * The specified path determines whether the tag exposes the status of the
 * bean itself (showing object-level errors), a specific bean property
 * (showing field errors), or a matching set of bean properties
 * (showing all corresponding field errors).
 *
 * <p>The {@link org.springframework.validation.Errors} object that has
 * been bound using this tag is exposed to collaborating tags, as well
 * as the bean property that this errors object applies to. Nested tags
 * such as the {@link TransformTag} can access those exposed properties.
 *
 * <table>
 * <caption>Attribute Summary</caption>
 * <thead>
 * <tr>
 * <th class="colFirst">Attribute</th>
 * <th class="colOne">Required?</th>
 * <th class="colOne">Runtime Expression?</th>
 * <th class="colLast">Description</th>
 * </tr>
 * </thead>
 * <tbody>
 * <tr class="altColor">
 * <td><p>htmlEscape</p></td>
 * <td><p>false</p></td>
 * <td><p>true</p></td>
 * <td><p>Set HTML escaping for this tag, as boolean value. Overrides the default
 * HTML escaping setting for the current page.</p></td>
 * </tr>
 * <tr class="rowColor">
 * <td><p>ignoreNestedPath</p></td>
 * <td><p>false</p></td>
 * <td><p>true</p></td>
 * <td><p>Set whether to ignore a nested path, if any.
 * Default is to not ignore.</p></td>
 * </tr>
 * <tr class="altColor">
 * <td><p>path</p></td>
 * <td><p>true</p></td>
 * <td><p>true</p></td>
 * <td><p>The path to the bean or bean property to bind status information for.
 * For instance account.name, company.address.zipCode or just employee. The status
 * object will exported to the page scope, specifically for this bean or bean
 * property</p></td>
 * </tr>
 * </tbody>
 * </table>
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see #setPath
 */
@SuppressWarnings("serial")
public class BindTag extends HtmlEscapingAwareTag implements EditorAwareTag {

    /**
     * Name of the exposed variable within the scope of this tag: "status".
     */
    public static final String STATUS_VARIABLE_NAME = "status";


    private String path = "";

    private boolean ignoreNestedPath = false;

    @Nullable
    private BindStatus status;

    @Nullable
    private Object previousPageStatus;

    @Nullable
    private Object previousRequestStatus;


    /**
     * Set the path that this tag should apply. Can be a bean (e.g. "person")
     * to get global errors, or a bean property (e.g. "person.name") to get
     * field errors (also supporting nested fields and "person.na*" mappings).
     * "person.*" will return all errors for the specified bean, both global
     * and field errors.
     *
     * @see org.springframework.validation.Errors#getGlobalErrors
     * @see org.springframework.validation.Errors#getFieldErrors
     */
    public void setPath(String path) {
        this.path = path;
    }

    /**
     * Return the path that this tag applies to.
     */
    public String getPath() {
        return this.path;
    }

    /**
     * Set whether to ignore a nested path, if any.
     * Default is to not ignore.
     */
    public void setIgnoreNestedPath(boolean ignoreNestedPath) {
        this.ignoreNestedPath = ignoreNestedPath;
    }

    /**
     * Return whether to ignore a nested path, if any.
     */
    public boolean isIgnoreNestedPath() {
        return this.ignoreNestedPath;
    }


    @Override
    protected final int doStartTagInternal() throws Exception {
        String resolvedPath = getPath();
        if (!isIgnoreNestedPath()) {
            String nestedPath = (String) pageContext.getAttribute(
                    NestedPathTag.NESTED_PATH_VARIABLE_NAME, PageContext.REQUEST_SCOPE);
            // only prepend if not already an absolute path
            if (nestedPath != null && !resolvedPath.startsWith(nestedPath) &&
                    !resolvedPath.equals(nestedPath.substring(0, nestedPath.length() - 1))) {
                resolvedPath = nestedPath + resolvedPath;
            }
        }

        try {
            this.status = new BindStatus(getRequestContext(), resolvedPath, isHtmlEscape());
        } catch (IllegalStateException ex) {
            throw new JspTagException(ex.getMessage());
        }

        // Save previous status values, for re-exposure at the end of this tag.
        this.previousPageStatus = pageContext.getAttribute(STATUS_VARIABLE_NAME, PageContext.PAGE_SCOPE);
        this.previousRequestStatus = pageContext.getAttribute(STATUS_VARIABLE_NAME, PageContext.REQUEST_SCOPE);

        // Expose this tag's status object as PageContext attribute,
        // making it available for JSP EL.
        pageContext.removeAttribute(STATUS_VARIABLE_NAME, PageContext.PAGE_SCOPE);
        pageContext.setAttribute(STATUS_VARIABLE_NAME, this.status, PageContext.REQUEST_SCOPE);

        return EVAL_BODY_INCLUDE;
    }

    @Override
    public int doEndTag() {
        // Reset previous status values.
        if (this.previousPageStatus != null) {
            pageContext.setAttribute(STATUS_VARIABLE_NAME, this.previousPageStatus, PageContext.PAGE_SCOPE);
        }
        if (this.previousRequestStatus != null) {
            pageContext.setAttribute(STATUS_VARIABLE_NAME, this.previousRequestStatus, PageContext.REQUEST_SCOPE);
        } else {
            pageContext.removeAttribute(STATUS_VARIABLE_NAME, PageContext.REQUEST_SCOPE);
        }
        return EVAL_PAGE;
    }


    /**
     * Return the current BindStatus.
     */
    private BindStatus getStatus() {
        Assert.state(this.status != null, "No current BindStatus");
        return this.status;
    }

    /**
     * Retrieve the property that this tag is currently bound to,
     * or {@code null} if bound to an object rather than a specific property.
     * Intended for cooperating nesting tags.
     *
     * @return the property that this tag is currently bound to,
     * or {@code null} if none
     */
    @Nullable
    public final String getProperty() {
        return getStatus().getExpression();
    }

    /**
     * Retrieve the Errors instance that this tag is currently bound to.
     * Intended for cooperating nesting tags.
     *
     * @return the current Errors instance, or {@code null} if none
     */
    @Nullable
    public final Errors getErrors() {
        return getStatus().getErrors();
    }

    @Override
    @Nullable
    public final PropertyEditor getEditor() {
        return getStatus().getEditor();
    }


    @Override
    public void doFinally() {
        super.doFinally();
        this.status = null;
        this.previousPageStatus = null;
        this.previousRequestStatus = null;
    }

}
